The invention relates to a pressure probe for detecting clathrates and the use thereof.
Inclusion compounds are referred to as clathrates (Latin: clatratus—latticed), wherein a guest molecule is enclosed inside a lattice formed by a host molecule. Naturally occurring inclusion compounds are the so-called gas hydrates, wherein gas molecules such as the methane molecules, but also carbon dioxide molecules or hydrogen sulfide molecules, are embedded as guests in a molecular lattice composed of water molecules. Inclusion compounds of methane gas in water (methane/water) are also referred to as methane hydrates or methane ice.
The forming of inclusion compounds in water or in sea water preferably occurs at high gas concentrations, at a low temperature, and with high pressure, in particular in sediments on the ocean floor where methane is formed locally as a result of the decomposition processes of bio-organic materials. Despite a specifically lower density of the gas hydrates (frequently also in the form of a sediment-gas hydrate-mixture), the adhesion to the subsurface or, specifically, heavy gas hydrate-free sediment ensures that the embedded and specifically lighter gas hydrate remains on the ocean floor. Gas hydrates were originally discovered, however, because of their capacity to clog natural gas pipelines in cold regions.
The existence of clathrates is generally detected via the acquisition of pressure/temperature and time diagrams for the respective inclusion compounds (e.g. methane/water) inside autoclaves (high-pressure measurements). Pressure/temperature diagrams, however, are frequently not precise and are subject to the typical thermo-dynamic delays. The detection with measuring technology is furthermore possible only inside a laboratory (autoclave), but not in situ or on location. No pressure/temperature diagrams furthermore exist in some cases, e.g. in the case of THF/water clathrates, since both components are liquids (see Y. Park, Y. N. Choi, S.-H. Yeon, and H. Lee, Thermal Expansivity of Tetrahydrofuran Clathrate Hydrate with Diatomic Guest Molecules, J. Phys. Chem. B, Vol. xxx, No. xx, XXX; P. W. Wilson, D. Lester, A. D. J. Haymet, Heterogeneous nucleation of clathrates from supercooled tetrahydrofuran (THF)/water mixtures, and the effect of an added catalyst, Chem. Eng. Sc. 60, 2937-41, 2005).
Clathrates in the form of liquid phases (e.g. THF/water) can be detected either optically with the aid of laser-infrared absorption or by means of viscosity measurements. However, optical testing requires special optical windows which can also be used under extreme pressure conditions, such as occur during the clathrate formation (for example 150 MPa for methane hydrate).
From the project entitled SUGAR—Submarine Gas Hydrate Storage Locations, Partial Project A2.2, “AKTIVE ELEKTROMAGNETIK ZUR EVALUIERUNG UND QUANTIFIZIERUNG VON GASHYDRATVORKOMMEN” [Active Electromagnetics For The Evaluation And Quantification Of Gas Hydrate Deposits], BMBF Funding No. 03G0688A, IFM-GEOMAR, Kiel, (http://www.ifm-geomar.de/index.php?id=sugar_a11000), it is known that high-frequency measurements on the ocean floor can be carried out with the aid of trailing antennas.
Japanese patent document JP 6 058 896 A discloses a device for detecting the clathrates of carbon dioxide with the aid of a conductivity sensor and a temperature sensor which are in thermal contact with a temperature control device.
German patent document DE 10 2006 022 290 A1 discloses a heater with an integrated temperature sensor on a substrate, wherein an electrically conductive thin-film layer on an insulating substructure is coated directly with an electrically conductive thin-film.
German patent document DE 10 2009 028 634 A1 describes a method for the production of a protective layer for resistance sensors, provided with a metal resistance layer, wherein the material for the protective layer is applied in such a way to the metal resistance layer that the particles of the protective layer are joined so as to form a porous protective layer.
International patent publication WO 2004/109807 A2 discloses materials that can be used for a dielectric layer on a semiconductor substrate, in particular silicon dioxide, silicon oxynitride, diamond, polymers and porous aluminum oxide.
A device is described in European patent document EP 2 024 077 B1 which can be used to record in the laboratory important parameters for the formation of clathrates, in particular the temperature, the pressure, the conductivity and the flow rate.